A New Technique for the Assessment of Intra-operative Femoral Component Rotation in Total Knee Arthroplasty: The Anterior Femoral Cortical Line

Accurate rotation of the femoral component in total knee arthroplasty is important for normal patella tracking, symmetrical patellofemoral joint contact, neutral varus-valgus positioning in flexion, correct rotational alignment of the tibia in extension and the avoidance of anterior femoral notching . Internal rotation of the femoral component causes a shift into valgus alignment with flexion and also an increase in the “quadriceps” (Q) angle with deleterious effects on patella tracking. Internal rotation of the femoral component also causes differences in the flexion and extension gaps by altering the relative dimensions of the posterior condyles in flexion. Flexion then causes asymmetrical tension across the prosthesis and gapping on the lateral side .